1. Technical Field
The present invention relates to a maintenance device for a liquid ejection head provided in a liquid ejection apparatus such as a printer, which performs maintenance for the liquid ejection head.
2. Background Art
A liquid ejection apparatus such as a printer includes, for example, a liquid ejection head (which is, for example, a recording head) having nozzles through which liquid is ejected. The apparatus performs printing by ejecting the liquid through the nozzles. As methods of printing employed by a recording head, there are scanning methods and non-scanning methods. In the scanning method, a recording head performs printing by ejecting droplets while being moved. The non-scanning method involves use of an elongated line head or a multiple head. The line head includes nozzle rows defined in the entire range corresponding to the maximum printing width. The multiple head is formed by a plurality of recording heads in which nozzle rows are provided over the aforementioned range. In the non-scanning method, a recording medium is transported in printing while the recording heads are fixed.
If ejection of ink through a liquid ejection nozzle is suspended for an extended period of time, the ink may become viscous or fixed in the nozzle and thus clog the nozzle. Thus, the printers disclosed in Japanese Laid-Open Patent Publication No. 8-281968, Japanese Patent No. 3155871, Japanese Laid-Open Patent Publication No. 2003-127434, Japanese Laid-Open Patent Publication No. 11-115275, Japanese Laid-Open Patent Publication No. 2002-264350, Japanese Laid-Open Patent Publication No. 2002-210983, and Japanese Laid-Open Patent Publication No. 2004-330495 include a maintenance device that performs maintenance for a recording head.
The maintenance device includes a cap and a suction pump. The cap is capable of sealing a surface (hereinafter, referred to as a “nozzle forming surface”) of the recording head in which nozzle openings are defined by contacting the nozzle forming surface in such a manner as to encompass the nozzle openings. The suction pump performs suction through the cap when the cap seals the nozzle forming surface, or generates negative pressure in the space sealed by the cap. This causes suction cleaning (suction recovery) in which ink (liquid) is drawn from the nozzles. In this manner, viscous ink and bubbles of ink are removed from the nozzles and the nozzles are recovered to a state in which the nozzles are capable of effective ink ejection. Further, the maintenance device has a wiper that wipes the nozzle forming surface. After the suction cleaning is completed, the wiper wipes the nozzle forming surface to remove ink or paper particles from the nozzle forming surface. Such wiping also functions to maintain the forms of meniscuses (hereinafter, referred to as “nozzle meniscuses”) of ink in the nozzles. Variation of the forms of the nozzle meniscuses causes variation of the amounts of liquid ejection and thus the sizes of printing dots, which lowers printing quality. However, by maintaining the nozzle meniscuses through wiping, desirable printing quality is saved.
For example, Japanese Laid-Open Patent Publication No. 8-281968 describes a maintenance device having caps arranged in correspondence with nozzle rows each of which ejects ink of a color. Ink suction is thus performed through the separate caps on the nozzle rows each of which ejects ink of a different color from the other nozzle rows. Further, in a maintenance device disclosed in Japanese Laid-Open Patent Publication No. 8-281968, a recording head for color inks and a recording head for black ink are wiped by separate wipers. Each of the wipers wipes the corresponding group of the recording heads when the recording head is moved in the scanning direction. When such wiping is performed, each wiper is raised to a wiping position and, in this state, the corresponding recording head is moved in the scanning direction relative to the wiper in such a manner that the nozzle forming surface of the recording head slides on the wiper.
Further, although suction cleaning is carried out usually as periodical cleaning that is repeatedly performed each time a constant time period elapses, defective ejection may be caused by a nozzle prematurely. Thus, it is desirable that a defective ejection nozzle be detected even before the periodical cleaning and cleaning be performed if a defective ejection nozzle is detected. As a device that detects such a defective ejection nozzle, a device using a laser beam described in Japanese Laid-Open Patent Publication No. 2002-210983 and a device detecting reflected light of light radiated onto a printed pattern disclosed in Japanese Laid-Open Patent Publication No. 2004-330495 are known.
However, the technique described in Japanese Laid-Open Patent Publication No. 8-281968 is inapplicable to wiping of a non-scanning type liquid ejection head such as a line head or a multiple head, since this type of liquid ejection head cannot be subjected to wiping involving movement of a recording head in a scanning direction.
If a defective ejection nozzle is detected by the detection device described in Japanese Laid-Open Patent Publication No. 2002-210983 or Japanese Laid-Open Patent Publication No. 2004-330495, the nozzle row including the detected nozzle is selected and subjected to suction cleaning. This reduces the consumption amount of the ink wasted through cleaning, not through printing. However, in this case, if wiping is carried out on the liquid ejection head by a single wiper as described in Japanese Laid-Open Patent Publication No. 8-281968, effectively operating nozzle rows that have not been subjected to suction cleaning are also wiped by the wiper. That is, idle wiping is performed on these effectively operating nozzle rows, urging the atmospheric air to enter the nozzles from between the distal end of the wiper and the nozzle meniscuses. The atmospheric air entering the nozzles cause pressure acting to deform the nozzle meniscuses, which induces defective ejection by the nozzles.